A trench-type metal-oxide-semiconductor (Trench MOS) transistor can be used as a power transistor.
The power trench MOS transistor distinctly differs from a typical MOS transistor in that a channel of the power trench MOS transistor is formed in a vertical direction, not a horizontal direction.
The power trench MOS transistor includes a vertical channel and a drain formed in a backside of a wafer as an output region.
The power trench MOS transistor is suitable for high-current and high-voltage operation using a small area. To apply a high voltage to the power trench MOS transistor, a lightly doped drain region (a drift region) is formed to a sufficiently large length.
Since electrons move vertically in the power trench MOS transistor, the lightly doped drain region (the drift region) can be vertically formed to increase a withstand voltage without increasing the area of a chip by adjusting a vertical doping profile. Therefore, high withstand-voltage and high-current operation can be possible using a small area.
Since the power trench MOS transistor is typically fabricated using a single layer silicon substrate, the power trench MOS transistor is suitable for a single product. However, the structure of the above described power trench MOS transistor does not easily provide a power trench MOS transistor on the same chip as a MOS transistor.